Neutron Inelastic Scattering Study of the Compound CeAl₃

Abstract

We have carried out time-of-flight inelastic scattering measurements on a polycrystalline CeAl₃ sample in the temperature range between 5K and 100K with neutrons of incident energy of 18.3 meV at a scattering angle of 7.5° (q_el = 0.4Å^-1). Our measurements at 5K reveal a broad double-humped spectrum on the neutron energy loss side which appears as if due to two broad upward transitions from the ground state to two higher-lying states at energies close to around 5.2 and 7.6 meV. With increasing temperature the double-humped structure is apparently replaced by a “single” broad peak with its centre of gravity shifting progressively towards lower energy transfers. A simple interpretation of the results in terms of transitions between normal crystal field split energy levels is not possible. However, allowing for the role of the strong s-f interaction, which could significantly modify the crystal field states, there are indications in the data that the ground state is composed principally of the 1 ± 3/2 > state with the other states having the character of the 1 ± 5/2 > and the 1 ± 1/2 > doublet states lying higher up in energy, in that order.